@peggyjs/coverage

Up the code coverage on your Peggy grammars, ensuring that the generated boilerplate code is covered in your unit tests. This makes it easier to find places in your grammar that actually need to be tested.

This library uses a few unsavory hacks to get to pieces of the Peggy boilerplate that are always included, even thought they aren't used in your particular grammar or in your configuration. For example, a few lines of code are only ever executed if you are in trace mode.

Installation

npm install --dev @peggyjs/coverage

API

Pass in the file: URL for the JavaScript output from Peggy:

await testPeggy(new URL("../lib/parser.js", import.meta.url), [
  {
    validInput: "foo",
    validResult: ["f", "o", "o"],
    invalidInput: "bar",
  }
]);

The second parameter is an array of tests. You should include at least one valid input, and at least one invalid input, but they need not be in the same test.

Each test definition has the following type:

export type PeggyTestOptions<T> = {
    /**
     * Which valid start rule to use?  Default: grammar
     * default start rule.
     */
    startRule?: string | undefined;
    /**
     * If specified, check this against the startRule.
     */
    validInput?: string | undefined;
    /**
     * What result should startRule return for validInput?
     * Default: validInput.
     */
    validResult?: T | undefined;
    /**
     * If specified, ensure that the grammar fails
     * on this input.
     */
    invalidInput?: string | undefined;
    /**
     * Expected peg$maxFailPos.
     */
    peg$maxFailPos?: number | undefined;
    /**
     * What to append to validInput to make it
     * invalid, so that library mode will return a prefix match.
     */
    invalid?: string | undefined;
    /**
     * Extra options to pass to parse(), overriding whatever else this library
     * would have otherwise used.
     */
    options?: (import("peggy").ParserOptions & ExtraParserOptions) | undefined;
};

Runtime support

Only tested on nodejs 18, 20, and 21. Only tested in es6 mode for now.